Lattice disorder and recombination centres in heat-treated FZ silicon

Thermal induced defects in high quality FZ silicon are studied. The principal aim of the work is to clarify the influence of dopant concentration on their generation and to observe the behaviour of carbon and residual impurities like heavy metals in the presence of very low oxygen contents. For low temperature heatings the most important mechanism responsible for lifetime deterioration in lightly and moderately doped silicon (cB < 1017 cm−3) is tentatively identified as FeB pair dissociation. At higher temperatures other mechanisms, like those associated with defect formation by thermal stresses and accidental contamination, can act, thus modifying the final effects on lifetime. For boron content higher than 1017 cm−3, heat treatments have only little effects on electrical parameters and crystal perfection of FZ silicon. Carbon (at the concentration commonly available in commercial high quality FZ silicon) do not have any direct influence on wafer annealing behaviour.